Sarah: Jack, what are you doing? Jack: Hang on a second. I'm just sending an email to a friend. Sarah: Informal letters and emails are the ones that we'd write to people that we knew well. For ...

While a formal invitation is something you would send to a client or a boss, you probably wouldn’t do this for a friend or co-worker. To them you would send an informal letter.

DEAR MISS MANNERS: If I invite someone to join me for an event via text or email, and they haven’t responded, how long should I wait before inviting someone else? Sending a casual invite with a ...